A major goal of current research in alloy development is the formulation of alloys exhibiting excellent strength properties, oxidation resistance, and good ductility over a wide range of temperatures; in particular at temperatures exceeding 1000.degree. C. Preferably, these alloys should be easy to fabricate and relatively inexpensive. To achieve these ends, superalloys based on either nickel or cobalt have been studied and developed over many years; however, in some present applications such as dynamic parts for gas turbine jet engines, the currently utilized nickelbase superalloys, age hardened by a Ni.sub.3 (Al,Ti) dispersion in the alloy, have reached their maximum effectiveness. An attractive alternative to the nickel superalloys are cobalt or cobalt-nickel based alloys containing carbides of Groups IV and V metals dispersed therein, particularly carbides of hafnium and zirconium.
Since it is known that the formation of small amounts of hafnium carbide in cobalt alloys improves high temperature properties, a method has been sought whereby the small amount of hafnium carbide in the alloy could be increased to a relatively large amount. Prior to the present invention, the addition of large amounts of hafnium (about 3%) has yielded alloys with large amounts of coarse carbides, coring and micro and macrosegregation of the hafnium carbide. These current hafnium containing alloys have large secondary dendrite arm spacings (on the order of 50 to 1000 microns) and are brittle, non-workable hot or cold, and inferior to the current nickel superalloys.
A further description of the background of the invention may be found in the doctoral thesis of inventor Robinson, entitled "Development of P/M Cobalt-Base Alloys Using Rapidly Quenched, Pre-Alloyed Powders", which is incorporated herein by reference. A copy of the thesis was filed with U.S. application Ser. No. 371,318 and a separate copy was deposited in the M.I.T. library system on or about Sept. 11, 1973. The work forming the basis of this thesis was conducted under the supervision of inventor Grant.
A number of different quenching techniques have been utilized in the formation of the superalloy powders and particulates. Quench rates for conventional ingot or precision casting processes are in the order of 10.sup.-2 .degree. to 10.sup.-1 .degree.C./second, whereas rates from 10.sup.2 .degree. to 10.sup.5 .degree. C. per second are reported for some atomizing and splat quenching processes. Common powder formation processes employ water, air, steam, and inert and soluble gases for disintegrating the molten metal into fine droplets to promote rapid quenching. Splat quenching (rapid solidification against a metallic substrate) can also be used. Generally, these processes involve bringing the molten mass to the liquid state and then disintegrating the melt into droplets or particulates to promote rapid solidification. The powders or particulates formed by these processes are then consolidated to full density (by hot isostatic pressing or hot extrusion, for example). The resultant wrought alloys show excellent properties and commercial potential.